720 Rule Calculator

FabRapid’s 720 Rule Calculator is a practical tool designed for managers, estimators, planners, and anodizing professionals. The “720 Rule” describes the relationship between the amount of electric current passed through an aluminum surface and the resulting thickness of the anodic oxide layer. According to research, it takes 720 amp-minutes of current per square foot of aluminum to produce one mil (0.001 inch or 25.4 microns) of anodic oxide (Westre 1997, 2000, 2017). At its core, the rule allows users to calculate the anodizing build rate, dwell time, or current density when any two of these parameters are known, enabling precise control over the anodizing process.